Hydrophones are the basic acoustic sensing elements used in underwater acoustic measurement systems. They are usually of a piezoelectric type and can utilize sensor elements made of PZT (lead zirconate titanate) piezoceramic material. Typically, two PZT sensors are used in each section of the hydrophone. Each of the PZT sensors is comprised of a PZT sensor element which has been bonded to a separate conductive, flexible, ductile bender element such as a metal or the like.
For optimum hydrophone performance, the total capacitance of the two PZT sensor elements in each of the hydrophone sections must be equal in order to assure equal sensitivity in each of the hydrophone sections.
The present invention relates to a piezoelectric sensor and, more specifically, to a PZT piezoceramic sensor element with a capacitance value which is preset by laser capacitance trimming of the PZT sensor element substrate and/or the substrate/bender element combination to assure that all of the hydrophone sensor elements have equal and matching capacitance values.